Sound waves are fluctuations in pressure that travel through a medium. When sound hits an object, it causes the surface of that object to move. Traditional microphones work by converting the motion of an internal diaphragm into an electrical signal. The diaphragm is designed to move readily with sound pressure so that its motion can be recorded and interpreted as audio. Laser microphones work on a similar principle, but instead of measuring motion of an internal diaphragm, laser microphones measure the motion of a distant object, essentially using the object as an external diaphragm.